Molded resistance.



UNITED STATES PATENT curios.

LAWRENCE E. BARRINGER, OF SOHENEGTADY, NEW YORK ASSIGNOR TO GENERAL ELECTRIC GOMPANY, A CORPORATION OF NEW YORK.

MoLDrin RESISTANCE.

1 No. 902,048. Specification of Letters was. Patented Oct. 27, 1908.

Application filed February 2, 1906. Serial No. 299,143.

To all whom it may concern.

Be it knownthat I, LAWRENCE E. BAR- RINGER, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certaln new and useful Improvements in. Molded Resistances, of which the following is a specification. 1

This invention relates to resistance conductors for electric circuits and has for its object the provision of a device of this character, the resistance of which may be varied within a considerable range by varying the composition and which at the same time will withstand a high temperature without ingury, in addition to having suflicient strength or general use and being exceedingly cheap,

efficient and durable.

My invention relates more 5 ecifically to what is known in the art as mol ed resistance sticks. This type of resistance has been well-known for some timebut has never been a success pfiactically, because of certain objections w 'ch it has been found difficult to overcome.

It is the object of m invention to overcome so far as possible t e objections hereto.- fore urged against this type of resistance.

In many of the types heretofore suggested a high temperature is essential to the harden- 1 mg of the compound. In others the comquantity of conducting pound air dries. The air-dried compounds require considerable time and do not produce the hard, dense, refractory substancewhich is required for general utilityin electrical work, while the fired or baked compounds are diflicult to make uniformly because of oxidation of the conducting material during baking 0r inequalities in shrinkage, producin varying resistance.

I have found that by mixin a conducting material with substances W ich may be treated so as to produce asilicate an exceedingly eflicient resistance stick may be produced. In carrying out my invention, therefore, I mix the desired uantity of the conducting substance, whio may'be graphite, magnetite, carborundum, or any similar conducting material in powdered or comminuted form, with suitable quantities of calcium or magnesium hydrate and silica, or flint. The material will of course vary with the resistance required and the amounts of the other materials may also be varied within aconsiderable range, de-

pendent upon the use to which the resistance is to be subjected. The percentage of conducting material may be as high as 70% or 80%, While asuitable proportion of calcium hydrate to flint in the com osition of the binding base may be approximately 2 to 3. After the materials are thoroughly mixed, the mixture is compressed to produce a dense mass. This mass is then subjected-to steam treatment, the pressure of which, and, therefore, the temperature, will depend somewhat u on the proportions of materials used and a so upon the time which is to be consumed in hardening. A pressure of 150 lbs. corresponding to a temperature of 181 C., has been found to be sufficient to harden certain compositions in about five hours. The steam converts the calcium hydrate and silica into a hydrous silicate of calcium, which makes a strong binder for the conducting material. As a substitute for calcium hydrate, I have found that powdered magnesium hydrate or magnesium oxid may be used.

.It be seen that I have produced a resistance stick having properties which render it valuable for use under a variety of conditions. It is exceedingly hard and strong and will stand a high temperature without injulrly. Many modifications of my invention w' suggest themselves to those skilled in the art, and it should be understood that I do not limit my invention to the combination of materials or the process of forming and arranging same herein mentioned, but that, all such modifications will come within the spirit of my invention in so far as they fall within the scope of the claims annexed to v 1 4. A resistance conductor comprising a steam-hardened'compound of a comminuted conducting material with silica and calcium hydrate.

5. A resistance conductor comprising a com ound of a comminuted conducting materia and hydrous silicate of calcium.

6. The rocess of making resistance conductors wliich consists in mixing a comminuted conducting material with suitable quantities of silica and a hydrate and subsequently treating the mixture to produce a hydrous silicate.

7. The rocess of making resistance conductors which consists in mixing a co1nn1inuted conducting material with suitable quantities of silica and a hydrate and subsequently treating the mixture with steam to harden the same.

8. The process of making resistance sticks which consists in mixing a comminuted coneoaoes ducting material with definite quantities of calcium hydrate and silica, compressing the mixture to produce a dense mass, and subsequently treating the mass with steam to harden the same.

9. The rocess of making resistance conductors Wl'llCh consists in mixing a comminuted conducting material with suitable quantities of silica and any base which will combine with it to form a hydrous silicate under the influence of steam treatment, and subsequently treating the mixture to produce a hydrous silicate.

In witness whereof, I have hereunto set my hand this 31st day of January, 1906.

LAWRENCE E. BARRINGER.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

